IBM Enterprise Storage Server 2105 E10, Introduction And Planning Manual

Page: 17 / 156

logical device A pointer to a logical volume on a storage server.
The pointer enables a host system to access the
logical volume. For the ESS, the logical device
represents a logical volume.
logical subsystem (LSS) The LSS is a logical “container” for RAID-5 arrays,
disk groups, and the volumes that are located on
those arrays or disk groups. One SSA Adapter
accesses an LSS primarily. One or more logical
subsystems can exist on the ESS. In general, the
ESS associates a given set of devices with only
one logical subsystem.
For System/390 hosts, a logical subsystem
represents a controller.
logical unit The Small Computer System Interface (SCSI) term
for a logical disk drive.
logical unit number (LUN) LUN is a SCSI term for the field in an identifying
message that is used to select a logical unit on a
given target.
logical volume The storage medium associated with a logical disk
drive. A logical volume typically resides on one or
more storage devices. For the ESS, you define this
unit of storage; the logical volume resides on a
RAID-5 array, and is spread over 6 + P or 7 + P
drives, where P is parity. A logical volume can also
reside on a non-RAID array on one storage device.
For CKD, you can define the logical volume size by
the device emulation mode (3390 or 3380 track
format). For UNIX
®
, Microsoft
®
Windows NT
®
, and
Microsoft Windows 2000
®
operating systems in the
fixed-block format, the size is 0.5 GB to 224 GB.
For AS/400
®
operating systems in the fixed-block
format, the size is 4.19, 8.59, 17.55, or 36 GB.
Note: The AIX
®
operating system views a logical
volume as a logical disk or a hard disk
(hdisk).
SCSI See
small computer system interface
.
SCSI host systems Identifies host systems that you attach to the ESS
with a SCSI interface. Such host systems run on
UNIX, OS/400, Windows NT, Windows 2000, or
Novell NetWare operating systems.
SCSI ID A unique identifier (ID) assigned to a SCSI device
that is used in protocols on the SCSI interface to
identify or select the device. The number of data
bits on the SCSI bus determines the number of
available SCSI IDs. A wide interface has 16 bits,
with 16 possible IDs. A SCSI device is either an
initiator or a target.
service personnel Individuals or a company that you have authorized
to service your ESS. This term also refers to a
About this guide
xv